1. Field of the Invention
The present invention relates to a resin composition, a resist underlayer film, a resist underlayer film-forming method, and a pattern-forming method.
2. Discussion of the Background
In manufacturing methods of integrated circuit elements, miniaturization of processing size using a multilayer resist process has progressed in order to achieve a higher degree of integration. In this process, a liquid resin composition for forming a resist underlayer film is first coated on a substrate, and thereafter a liquid photoresist composition is further coated. Next, a mask pattern is transferred using a reduced projection exposure system (stepper) and developed with an appropriate developer solution to obtain a resist pattern. Subsequently, the resist pattern is transferred to the resist underlayer film by dry etching. Finally, the resist underlayer film pattern is transferred to the substrate by dry etching, whereby a substrate provided with a desired pattern can be obtained. In this process, a multilayer process in which one type of a resist underlayer film is used may be referred to as “two-layer resist process”, whereas a multilayer process in which two types of resist underlayer films are used may be referred to as “three-layer resist process”.
In general, resist underlayer films have a function as an antireflective film that absorbs radioactive rays reflected from the substrate. Also, a material having a high carbon content is generally used for resist underlayer films positioned immediately on the substrate. When the carbon content is high, etching selectivity upon processing of the substrate is improved, and thus more accurate pattern transfer is enabled. As such underlayer films, in particular, thermosetting phenol novolak resins have been well known. In addition, it is known that compositions containing an acenaphthylene polymer exhibit favorable characteristics as an underlayer film (see Japanese Unexamined Patent Application, Publication Nos. 2000-143937 and 2001-40293).